As one example of the packing box, a packing case is conventionally known that includes an arc-like cutout portion formed at an upper end of a front face of box body overlapping an insertion piece and a push-in piece formed at a portion of the box body facing the cutout portion and surrounded with an arc-like cut so that a finger hook hole can be created, wherein the packing case is opened by hooking a finger into the finger hooking hole and pulling up a lid portion (see Patent Literature 1, for example).
As another example of the packing box, an article storage box is known that includes cut lines (slits) provided at both ends of a border between a lid plate and an insertion piece and side flaps, wherein the article storage has a so-called slit lock structure in which the side flaps are hooked into the cut lines (slits) (see Patent Literatures 2 and 3, for example).
As another example of the packing box, a sealed box is known that includes locking cuts formed at both end portions of a lateral folding line between a top face flap piece and a top face insertion flap piece and constituting a lock mechanism, locking projection pieces formed at base ends of inner top face flap pieces and constituting the lock mechanism, and a flange formed at a center portion of the top face flap piece and used as a start portion of tearing along tear inducing lines (see Patent Literature 4, for example).
In a state in which the top face flap piece closes an opening of a tubular body, the top face insertion flap piece is anchored by inserting locking projection pieces into the locking cuts so that the state in which the top face flap piece closes the opening is maintained. An article stored in the sealed box can be taken out by tearing along the tear inducing lines.
As another example of the packing box, a paper box is known that locks a lid plate in a closed state by engaging base portions at both ends of an insertion piece to front edge portions of lid pieces (side flaps) (see Patent Literature 5, for example). The paper box is opened by pushing a push-in portion, which is formed at a front portion of the lid plate with a folding line or a cut line, by a finger to create a depressed area and then inserting the finger into the depressed area to lift up the lid plate by the finger to unlock the lid plate.